1. Field of the Invention
The present invention relates to a heat radiating louver fin for a heat exchanger, and more particularly to a louver fin in which a strip thin sheet is formed into a corrugated shape configured alternately and continuously by bent portions and flat portions where louvers are formed, and also to a corrugation cutter for forming such a louver fin.
2. Description of the Related Art
A heat exchanger such as a radiator mounted on an internal combustion engine vehicle, or that such as a heater core, a condenser, or an evaporator of an air conditioner is configured so as to efficiently perform the heat exchange function with the outside air via fins disposed in the heat exchanger.
FIG. 15 shows a conventional fin 1. A strip thin sheet 2 is formed by using a corrugation cutter (not shown) into a louver fin wherein a corrugated shape (bellows-like shape) in which bent portions 1a and flat portions 1b are alternately continued, and a plurality of louvers 3 are punched and raised in each of the flat portions 1b along the longitudinal direction Y of the strip thin sheet 2 to be arranged in the width direction X of the strip thin sheet 2.
When the louvers 3 are punched and raised in the louver fin 1, as shown in FIG. 16, the distortion amount of an outer cut end 3b of each of the bent portions 1a is larger than that of an inner cut end 3a. Such distortion amounts of the bent portions are accumulated in the longitudinal direction of the louver fin 1. As a result, apex twist occurs in the bent portions 1a, and the whole of the louver fin 1 is curved and rounded as shown in FIG. 17.
When the louver fin 1 is rounded as described above, there becomes impossible to mount the louver fin on a heat exchanger. As shown in FIG. 15, conventionally, the louvers 3 formed in each of the flat portions 1b are therefore divided into groups A and B so that raised directions of the louvers are symmetrical in the width direction X of the strip thin sheet 2. The louvers 3 of the group A are opened toward the front side, and the louvers 3 of the group B are opened toward the rear side, whereby the distortion amounts due to the punching and raising process are uniformalized in the width direction X so as to maintain the linearity of the louver fin 1.
When the louvers 3 in each of the flat portions 1b are punched and raised in different directions or opened in different directions, however, the airflow passes through the louver fin 1 with following a meandering path, so that the flow resistance is increased and hence the amount of passing air is reduced to lower the heat exchange efficiency.